The present invention relates to a pumping set in particular for an ABS/ASR/VSC brake system (antilock braking system/automatic slip regulation/vehicle stability control system) for off-road vehicles.
From WO 97/48583 a radial piston pump is known, having an electric motor which drives a piston pump arrangement. To keep any leaking hydraulic fluid away from the electric is motor, in the housing of the piston pump arrangement collecting chambers and channels are formed, into which leaking hydraulic fluid passes under the action of gravitational and/or centrifugal force in order to be stored there. Disposed between the electric motor and the piston pump arrangement is an open rolling-contact bearing and disposed at the side of the rolling-contact bearing facing the electric motor is a slinger, which is driven by the electric motor. Leaking hydraulic fluid, after it has passed through the open rolling-contact bearing, is kept away from the electric motor by means of the slinger. Said radial piston pump may be installed only with a horizontal orientation (with the electric motor next to the piston pump arrangement) or with a vertical orientation such that the electric motor is disposed above the piston pump arrangement, for, if the radial piston pump were to be installed with the electric motor below the piston pump arrangement, the hydraulic fluid under the action of gravitational force alone would flow out of the collecting chambers and the channels into the electric motor, particularly when the electric motor was stopped and the slinger was not driven.
With such pumping sets there is also the problem that because of temperature variations between the interior of the electric motor and the space, in which the eccentric pump arrangement is situated, a (short-term) differential pressure of up to 2 bar may arise. As a result, excess hydraulic fluid is sucked out of the space, in which the leakage of the eccentric pump arrangement is situated, through the ball bearing or needle bearing for the output shaft and into the interior of the electric motor. Particularly in the event of extended operating times of the pumping set (due to operation of a vehicle stability control system), a significant quantity of hydraulic fluid may escape and be drawn into the electric motor by a vacuum, which arises in the electric motor as a result of short-term cooling (caused by splashwater getting onto the electric motor) in the interior of the electric motor.
Conventional sealing methods (sealing rings, sealed bearings etc.) are too expensive and also do not prevent the hydraulic fluid from being dispersed into the environment.
Thus, the arrangement is also not immersion-proof (e.g. for off-road vehicles).
The invention seeks to solve the problem of achieving optimum utilization of the installation space in a vehicle and in particular of overcoming the drawbacks described above.
To solve said problem, the invention proposes a pumping set, in particular for an ABS/ASR/VSC brake system.
The storage chamber disposed according to the invention in a pumping set may store hydraulic fluid which escapes from the piston even when the pumping set is disposed with the electric motor below the piston pump arrangement. The pumping set according to the invention may therefore also be installed in said position into a vehicle. The installation space in the vehicle may therefore be utilized to better effect.
In a preferred embodiment, the electric motor in its end region facing the piston pump arrangement has a recess, which forms the storage chamber.
In the radial piston pump described in WO 97/48583 all of the channels and collecting chambers are formed in the housing of the piston pump arrangement. In contrast, according to the invention a dead space in the electric motor may be used as a storage chamber, thereby reducing the total volume of the pumping set.
To prevent hydraulic fluid from running out of the storage chamber in the event of shaking of the pumping set (due to operation of the motor vehicle under rough conditions), the storage chamber is at least partially filled with a material which absorbs hydraulic fluid.
In a preferred embodiment of the invention, the storage chamber surrounds the output shaft of the electric motor at least in the shape of graduated circle.
In an identical manner, the collecting region preferably at least partially surrounds the output shaft of the electric motor.
By virtue of said arrangement it is ensured that hydraulic fluid escaping from the pump arrangement passes reliably into the collecting region and from there into the storage chamber.
In a currently preferred embodiment, the output shaft of the electric motor is additionally provided with a centrifugal body, which is non-rotatably connected to the output shaft and is in such a spatial relationship to the piston pump arrangement that hydraulic fluid escaping from the piston pump arrangement during operation may pass onto the centrifugal body in order to be slung by the latter into the collecting region. This prevents hydraulic fluid from being able to pass along the output shaft (through the bearing situated in the end region of the electric motor) into the interior of the electric motor.
The pumping unit is moreover devised so as to be disposed with a substantially vertically oriented output shaft in a motor vehicle, wherein a slight inclination of up to around 25xc2x0, preferably of up to around 15xc2x0 in the direction of the collecting region may be provided. Said measure also ensures that hydraulic fluid escaping from the pump arrangement does not pass into regions outside of the collecting region or the storage chamber.
When according to a preferred embodiment the interior of the electric motor is connected to the piston pump arrangement by a vent opening, which is situated in the end region facing the piston pump arrangement, to the piston pump arrangement, a pressure compensation between said two regions may easily occur. Thus, the electric motor is moreover immersion-proof and suitable for installation in the engine compartment of a motor vehicle.